Rectifier assembly of the dry disk type



June 24, 1952 R. H. BLAIR RECTIFIER ASSEMBLY OF THE DRY DISK TYPE Filed Nov. 27, 1948 ROBERT H. BLAIR Patented June 24, 1 952 UNITED STATES PATENT OF F ICE Robert Remain-Warren, Ohio, assignor to The "Taylor winficld Corporation, Warren; Ohio; a

: "corporation of "Ohio Application November 27; 19 1's," seriai Nol 62,258

8 Claims.

This invention relatesto animproved rectifier assembly ofthe'dry' disctypeu 'seful' in'the electric resistance"welding art, for example;iand more particularly to" an improved" electric translating means of the voltage 'reducingfl'and rectifier type for furnishing a"heavy"unidirect1onal welding current from" the output terminals: of the welding transformer p'r transformers'through the rectifiers and into the current "conductive supports for the welding electrodesfandin this regard it is a further'objectfofg the invention to provide an improved' 'as'semblybf a transformer and a rectifier, :useful injresi's'tance welding, which is more compact vinfn ature toiacilitate installation in machinesQandwh ich is possessed of greater mechanicalstrengthand' rigidity than combined apparatus"heretofore' proposed for the samepurpose. 7 v I H v Another'object of the invention 'isitheprdvision of an improved assemblyeo'mprising a power transformer of the wading type and a dry type of rectifier connectedwith'the secondary turns thereof which is "or improvedelectricalj characteristics, particularly as regards, lower inductive reactance and fa lowerfl R loss in" the conduction of the current from the terminal pads of the secondary turns of the transformer through the rectifier to T the welding electrodes. The loweringofthe e'vereu impedancelsadvantageous, of cours rrem' thelstandpoint of efliciency of operation but 1 of equal orv greater benefit is the substantial redfictionlof iinjducltive reactance in the "loadcircuit fconnecte'd with the "secondary turns or'the "welding "transformer or transformers. The p'o'wer factor infthesystem is materially improv'ed'and ininstallati'ons utilizing a multi phas e pd wer sourcethe"load is more equally balanced between the respective phases. Further, "all "these factors contribute" to precision of control,'the capability of which is one of the more -advantageousfactors*oi' -thedirect' current resistance welder.

ffYet anotherfobjectbf "the invention is the pr'ovision ina rectifier assembly of the dry disc typeQQf' an improved arrangement for g'anging and rnounting' the dry type of rectifiers' em- "ployed'and' ofirnproved means for cooling the rectifier bank. Heretofore such 'rectifiers have been eooledf' by convection streams of air forced "through 'the'interstices' of the rectifier bani; and under this method the; current 1 transmission characteristic of the ban may vary quite widely. 'Thepresent invention'prbvides a practical arrangernent ior frriaiiitaining the rectifier ele- 'ments at 'a' fairlyuni'form temperature and this is accomplished by cooling "the rectifier I bank principally by concluction of the heat generated to 'iiowing streams'of water rather'than by conve'ctionfasheretofore.

Astill iurther object ofjthe inventionis the provision of 'anfimproved dry discjtype of rectifier assembly" ha'ving"particular" applicability, in

' the resistance weldin'g field'; which is highly versatile in its'ap'pli'cation in'that it is in the nature 7 of "a small compact"unitaryassembly' which may be employed either singly or in multiple for use in welding equipment of different capacities. Thus; for small machines only'a single phase of the commercial sourceimaybe" employed, in intermediate machines "onlya single assembly may be employed in each of the three pha'sesfl'of the source, while in largeflmachinejs two ormore of the standardized assemblies] may "be employed in' each of the respective phases.

The aboveand other objects and advantages of the invention will become apparent upon consideration of the following detailed specification and the "accompanying drawing wherein there is disclosed a preferred embodiment of the invention.

'Figur'el is a planview of an assembled electric resistance welding unitconstr'ucted in accordan'ce with the principles'of my'invention and comprisingja transformer, a rectifier of the stacked dry disc type anda connected pair of welding'electrodes. Figure 1 also indicates, in

d0ite .,9 it n i owt qb er assemblies of a ,t f mer nd rec er m be pled to may be provided with four primary winding coils II for variably connecting to one of the phases of the power source to determine the output voltage of the transformer. Sandwiched between the coils H are the secondary turns l2 which, in accordance with usual construction, are of cast construction, being cast in multiple and integral with the terminal pads 13 and M. The outer peripheral edges of the terminal pads I3 and it are grooved to receive the cooling water conducting tubes l5 which are made of material having good heat conducting properties such as copper, for example. Tubes [5 are held in position by brazing as will be understood.

The rectifier illustrated is of the full wave type and it is assembled on the pads l6 and H which are adapted to overlie the transformer secondary pads l3 and M respectively, in fiat abutting relation, and to be rigidly secured to the pads l3 and M by suitable means, not shown. The rectifier comprises essentially a multiplicity of stacks of metallic discs l8 which are securely clamped between a plurality of spaced parallel current conductive plates or fins and in practice the rectifier elements I 8 may be comprised of copper discs each having a layer of cuprous oxide on one of its faces and, of course, all the discs in each element l8 are oriented to face in the same direction so that current will readily pass in one direction while being impeded in the opposite U direction. The supporting and connecting fins must be not only good current conductors but in accordance with this invention should be equally efficient heat conductors and in addition should possess good physical strength. These requirements are satisfied by hard drawn sheet copper having a thickness of .125 inch where the height of the fin is approximately eight inches and its length twelve inches. Each of the fins, designated herein by reference numeral I9, is formed with a laterally extending foot for electrical and physical connection to either of the two pads i6 and I! or to either of each of the direct current bus bars 2| and 22 positioned opposite the pads Hi and 11. Thus to provide a uni-directional path between the pad i6 and the bar 2| one each of three spaced pairs of adjacent fins is connected to the pad l6 while the other fin of each pair is connected to the bar 2|. Clamped intermediate the fins of each of these pairs are twelve of the rectifying disc elements l8 and in this manner the rectifying assembly shown schematically at 23 in Figure 3 may be attained. By similar analysis it can be observed that a second uni-directional path is made possible between the pad [5 and the bar 22 while two oppositely disposed uni-directional paths are provided between the pad I? and the bars 2| and 22. The discs l8 and the fins |9 are tightly clamped together into a compact unit by the bolts 24 which, of course, are suitably insulated with respect to the various discs and fins. The laterally extending feet 20 of the fins H] are adapted to be rigidly but detachably connected to the pads l6, i i and to the bars 2| and 22 by any suitable means such as cap screws, not shown, and in practice the rectifier bank is assembled with the outer faces of the feet 20 at one end of the unit lying accurately in a common plane while the outer faces of the feet 20 at the other end of the unit lie accurately in a spaced parallel plane. Further, such faces are preferably silver plated so that high efiicient electric and heat conductive interconnections are effected between the fins and the pads and bars. Now if the pads i6 and l! are of uniform thickness and if the outer faces of the transformer secondary terminal pads l3 and M are faced to lie accurately in a common plane it will be obvious that the highly efficient electrical connections will be made between the transformer secondaries and the rectifier assembly. The same is also true as regards the rectifier assembly and the bus bars 2| and 22, assuming that the mounted bases of the bars are smoothly surfaced.

Extending about the periphery of the mounting pad l8 and in intimate contact therewith is a tube 25 for conducting cooling liquid and a similar tube 28 is similarly positioned on the periphery of the pad H. A similar tube 2'! extends along the upper edge of the bar 2| and a similar tube 28 extends along the lower edge of the bar 22. The tubes 25-48 are preferably constructed of copper for good heat conductivity and to increase the conduction of heat as well as to provide rigid mounting for the tubes the edges of the pads I6, I! and of the bars 2|, 22 may be grooved to receive a portion of the tubes and the tubes may be brazed in position in these grooves as is well understood in the welding machine art.

In the practical use of the invention a suitably supported and normally fixed electrode 29 is ar ranged to be electrically connected to the current conductive bar 22 by means of suitable low impedance connectors and a movable electrode 30 is arranged to be electrically connected with the bar 29 through a flexible current conductive band 3 I.

For small machines but a single phase of the power source will be utilized and in this case the bars 2| and 22 will be quite shortbeing of a length merely to cover all the lugs 20 of the fins IQ of the rectifier pack. For three-phase operation of larger machines three of the transformers and rectifier assemblies will be utilized in the manner suggested by the full and dotted lines of Figure 1 and in this case the direct current conducting bars 2| and 22 will have a longer length sufiicient to cover all the lugs 20 of each of the three rectifier packs.

Since the current conductive plates or fins IQ of the rectifier pack are closely coupled with the secondary turns of the transformer |0|2 and are in effect mounted directly on the terminal pads of the secondary turns the secondary or load circuit of the transformer will have a minimum of inductive impedance and consequently the system will have a high current rating. In prior rectifying systems heretofore proposed for resistance welding purposes quite long and looped conductors have been employed for connecting the transformer secondary with the input terminals of the rectifier, resulting in substantial inductive reactance in the power circuit. It should also be observed that the substantial areas of contact between the plates IS, IT and the pads l3, l4 and between the feet 20 of the fins l9 and the plate l6, [1, 2| and 22 together with the closeness of the couplings and the short longitudinal dimensions of the fins l9 results in current paths of extremely low resistance which further favors the flow of the welding current and the overall efficiency of the system. In addition to these considerations of desirable electrical characteristics the disclosed arrangement of the components of the system is highly advantageous from a mechanical standpoint in reducing the quantities of copper and other materials required in providing a combined unit which may readily be incorporated in a welding machine housing of practical dimensions, and in providing a pre-assembled standardized power unit for powering; direct current welders of widely varying capacities from a commercial alternating current "source.

In the practice of the inventionthe rectifier pack or packs will preferably be so positioned that the fins l9 will lie in vertical'planes to facilitate the circulation of air upwardly through the interstices between the fins I9 and discs [8 and this upward convection current will normally be suificient to cool the centerpart of the pack or packs. However, in accordance with this invention principal reliance is placedon the water cooling tubes to conduct the excess heat away from the rectifiers. Since the fins l9. are short in length, of appreciable mass, are formed of material having good heat conduct n qualities, and are intimately bonded to the copper plates I6, 11 and bars 2| and 22 heat will be more efficiently transmitted from any part of the rectifier pack to the plates and bars mentioned and by cooling each of these plates and bars in the manner above explained the excess heat will be readily carried away. Further, by controlling the volume of the cooling fluid passed through the tubes 25-28 or by regulating its temperature the temperature rise of the rectifier electrodes may be kept between predetermined limits for uniformity of operation of the welding machine.

The above specifically described embodiment of the invention should be considered as illustrative only as obviously many changes may be made therein without departing from the spirit or scope of the invention. For example, instead of forming the right-angularly disposed feet on the fins l8 and I9 for connection to the bus bars 2|, 22 and the copper plates I6, I! these parts and bars may be formed with slotted extensions into which straight fins are fitted for mechanical and electrical connection. Also the transformer pads (l3 and f4) themselves may receive the rectifier fins directly either in slots as mentioned or on a flat surface as shown and it should therefore be understood that the prime consideration of the invention is the close and adequate coupling of the rectifier banks on the welding transformers. Flat connections between straight rectifier fins and the bus bars and transformer pads may also be effected without the use of slots.

An important feature of the invention is the fact that the rectifier is water-cooled at both ends and air-cooled at its middle portion whereby the rectifier may be operated under heavy load for long periods without deterioration.

It should be obvious that the power packs described herein, each comprised of a single phase welding transformer and a single phase full-wave rectifier may be connected to the power sup-ply, to each other, and to the welding electrodes in a large number of specific arrangements, depending on requirements as to capacity, current fluctuation, etc. Thus, I may employ a delta connection between the power supply and the transformer primaries and in some applications where a high average DC current is desired I may employ in the same machine one bank of packs connected in delta and another bank of packs connected in Y to give a resultant DC output having twelve phase characteristics. This highly persistent current flow is desirable in certain resistance welding applications. Another possible modification is the closing of the secondary circuits of the welding transformer in delta by means of low impedance strap -conductors toproduce three-phase full-wave rectification.

While the direct current power supply of the invention comprised of a transformer, a rectifier pack, and cooling means therefor is of special utility in electric resistance welding machines and has been so described above it should be-noted that the assembly is equally applicable to other specific uses requiring heavy direct currents of low voltage such as in electroplating equipment, for example.

Reference should be had tothe appended claims in determining the scope of the invention.

I claim:

1. A rectifier assembly comprising aplurality of longitudinally disposed spaced-parallel current-conducting fin lying in vertical planes and connected at one of their ends to a pair of currentconductive plates spaced one above the other and lying in a common vertical plane and disposed transversely with respect to the vertical planes of said fins, a plurality of dry disc rectifier elements clamped between said fins, said plates being adapted to be detachably secured to the secondary terminal pads of a welding transformer, the opposite end portions of said fins being bent transversely to provide integral connecting lugs lying in a common plane for connection to a pair of transversely disposed and vertically spaced current-conducting bus bars.

2. In electric resistance welding apparatus. the combination of a welding transformer having water-cooled secondary terminal pads, watercooled bus bars spaced outwardly from said pads, and a rectifier assembly interposed between said pads and bars and comprising a plurality of spaced current-conducting fins connected with said pads and bars, dry disc rectifier elements clamped between said fins, the arrangement being such that said assembly i cooled by the flow of air between said fins and by the conduction of heat along said fins to both said pads and bars.

3. Apparatus according to claim 6 further characterized in that said assembly comprises a pair of current-conducting plates secured to one end of said fins, said plates overlying said pads in intimate contact therewith, and means to cool said plates by a flowing stream of cooling fluid.

4. In electric resistance welding apparatus the combination of a transformer having a U-shaped secondary winding with each end of said winding having an outwardly facing terminal pad, a pair of current-conducting plates disposed substantially parallel to the outer faces of said pads and spaced outwardly therefrom, a plurality of spaced parallel current-conducting plates interconnecting said pads and said first mentioned plates in both heat exchanging and current-conducting relation therewith, a plurality of dry disc rectifier elements clamped between said second mentioned plates, each of said second mentioned plates being rigidly connected at one end to one of said pads in fiat overlying relation therewith.

5. Apparatus according to claim 4 further characterized in that the other ends of said second mentioned plates are rigidly connected to said first mentioned plates in fiat overlying relation therewith.

6. Apparatus according to claim 4. further characterized in that said second mentioned plates lie in vertical planes whereby said rectifier assembly may be cooled by an upward flow of air through the interstices existent in said second mentioned plates and said elements.

7. Apparatus according to claim 4 further including liquid conducting tubes extending along the outer peripheral edges of said first mentioned plates for conducting cooling liquid, said tubes being constructed of material having good heat conducting properties and being mounted in intimate contact with the material of said first mentioned plates substantially throughout the length of said tubes.

8. A rectifier assembly of the dry disc type comprising a plurality of spaced parallel currentconducting plates, a plurality of dry disc rectifier elements clamped between said plates, a pair of current-input pads rigidly connected to one end of said plates and having fiat overlying relation 15 2,119,381

8 overlying relation with substantial surface areas of the plates, and means to conduct cooling fluid in heat exchanging relation to said pads and bar whereby heat generated by said elements will be extracted through said plates and connections into said pads and bars.

ROBERT H. BLAIR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Cheeseman et al. May 31, 1938 2,175,841 Kafka et a1 Oct. 10, 1939 2,412,989 Kotterman Dec. 24, 1946 

